Isaac Prompts NASA to Bump Radiation Mission Launch to Thursday

NASA will look to Thursday -- Aug. 30 -- for a third attempt to launch the Radiation Belt Storm Probe mission to avoid gusty winds and other storm threats posed by Tropical Storm Isaac.

Efforts to launch the $686 million twin spacecraft mission from Cape Canaveral Air Force Station, Fla., were scrubbed for a second time early Saturday by the threat of off shore thunderstorms.

The bid Thursday to place the two 1,400 pound probes in orbit atop a United Launch Alliance Atlas 5 401 rocket from Space Launch Complex-41 is scheduled for 4:05 a.m., EDT, the start of a 20 minute window.

The Atlas 5 will be rolled back from Space Launch Complex-41 to the Vertical Integration Facility at CCAFS until Isaac clears the Florida peninsula, NASA managers decided after Saturday's scrub. The launch had been tentatively re-set for early Sunday.

The first attempt to start the two-year study of high energy particle fluctuations in the Earth's twin Van Allen radiation belts was scrubbed on Friday by a drift in frequency noted in the C-band transponder on the Atlas 5.

Mission managers elected to proceed with the defective hardware but activated additional ground-based C-band radar tracking assets for the ascent.

Saturday's countdown reached a prolonged four-minute hold without technical issues. Lift off was scheduled for 4:07 a.m. The scrub was called as the 20 minute launch period expired because of threats from lightning and a cumulus clouds in the flight path.